>The design of this year’s Nightmare monster was handled by Tomo Hyakutake, who is also behind the designs of several Ultraman monsters and the films in the Shin Japan Hero Universe.
>According to him, the general requirement for this year’s Nightmares was to design asymmetrical arms to reflect the imagery of nightmares. Early on, there was even an idea to incorporate the image of Sigmund Freud, the pioneer of modern psychological dream research, into the design.
>For the Gun Nightmare in episode 01, if you pay close attention, you will notice it was designed to evoke Shocker’s Man Spider from the very first Kamen Rider series, especially in the eye area.
He didn't mention anything about the suits being based on previous riders.

The art is infinitely more terrifying than the actual suit